The present invention relates to a process of preparation of viscous water as well as to the viscous water produced by this process. This water is principally used in oil extraction.
Many processes are already known for maintaining oil wells in active service; amongst these there can be mentioned that comprising injecting viscous water into the wells. Viscous water is so-called due to the fact that there are added to the water, salted or not, thickening agents such as polyacrylamides, which are petrochemical products, or xanthan gums.
These last are provided from the fermentation of carbon-containing substrates by bacteria of the species Xanthomonas according to the process first described in U.S. Pat. No. 3,000,790 and then improved on in numerous U.S. Pat. Nos. 3,020,206, 3,391,060, 3,427,226, 3,433,708, 3,271,267, 3,251,749, 3,281,329, 3,455,760, 3,565,763, 3,594,280 and 3,391,061. The use of viscous solutions of xanthan gums in the recovery of oil is described in numerous U.S. Pat. Nos. 3,243,000, 3,198,268, 3,532,166, 3,305,016, 3,251,417, 3,391,060, 3,319,715, 3,373,810, 3,434,542, 3,729,460, 3,853,771, 4,010,071 and 4,119,546.
It is to be noted that all this literature treats in diverse fashion the use or improvement of the xanthan gums obtained in a discontinuous operation which extends generally for two to four days during which bacteria of the species Xanthomonas campestries are fermented on carbohydrate substrates such as molasses, by-products of the sugar industry, or glucose syrup resulting from the hydrolysis of starch. On the other hand, U.S. Pat. No. 3,965,985 describes a process, also discontinuous, for obtaining viscous water, which uses various micro-organisms capable of fermenting oxygenated compounds of petroleum fractions, such as aldehydes or methanol.
The discontinuous production of a chemical or biochemical product is much more onerous than continuous production and up to now the high cost of xanthan gums produced by discontinuous fermentation has in practice prohibited their use in assisting oil recovery, despite all the improvements imparted to this product by the references cited above. Therefore the essential aim of the present invention is a process for preparing viscous water in continuous fashion, that is to say cheaply.
Another aim of the invention is the use of genera of bacteria other than the Xanthomonas using the same carbohydrate substrates, sugars, glucose or starch hydrolysates.
Another aim of the invention is a process of this type which can be put into operation near oilfields. An object of the invention is a viscous water prepared according to such a process having properties equal to or superior to those prepared by the previously known processes.